feat(decorator-pattern): 实现文件输入流的缓冲装饰器- 新增 MyFileInputStreamBuffer 类，用于缓冲文件输入流

- 创建 App 类，演示使用缓冲装饰器读取文件的性能提升- 添加 .gitignore 文件，忽略 IDE 和构建工具的配置文件- 创建 Maven 项目配置文件 pom.xml

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>feng.yu</groupId>
+    <artifactId>shengsheng_study</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

src/main/java/decorator_pattern/app/App.java

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+package decorator_pattern.app;
+
+import decorator_pattern.tech.MyFileInputStreamBuffer;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.time.Instant;
+
+/**
+ * @author weizhenfeng韦振凤
+ * @version 1.0
+ * @description: TODO
+ * @date 2025/6/2 下午9:51
+ */
+public class App {
+
+    public static void main(String[] args) {
+        unOpt();
+
+        opt();
+
+    }
+
+    private static void opt() {
+        File file = new File("F:\\BigData\\交易模型\\交易模型-存款交易信息.xlsx");
+        long startTime = Instant.now().toEpochMilli();
+
+        try (
+                InputStream fis = Files.newInputStream(file.toPath());
+                InputStream bufferedStream = new MyFileInputStreamBuffer(fis) // 使用缓冲装饰器
+        ) {
+            while (bufferedStream.read() != -1) {
+                // 空循环
+            }
+            System.out.println("缓冲读取耗时(ms): " + (Instant.now().toEpochMilli() - startTime));
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    private static void unOpt() {
+        File file = new File("F:\\BigData\\交易模型\\交易模型-存款交易信息.xlsx");
+        long epochMilli = Instant.now().toEpochMilli();
+        try (FileInputStream fileInputStream = new FileInputStream(file)) {
+            while (fileInputStream.read() != -1) {
+                if (fileInputStream.read() == -1) {
+                    break;
+                }
+            }
+            System.out.println(Instant.now().toEpochMilli() - epochMilli);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+}

src/main/java/decorator_pattern/tech/MyFileInputStreamBuffer.java

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+package decorator_pattern.tech;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class MyFileInputStreamBuffer extends InputStream {
+
+    private final InputStream decoratedInputStream;  // 被装饰的InputStream
+    private final byte[] buffer = new byte[8192];   // 缓冲区
+    private int position;     // 当前缓冲区位置
+    private int count;        // 缓冲区有效字节数
+
+    // 使用InputStream而不是具体FileInputStream，提高通用性
+    public MyFileInputStreamBuffer(InputStream inputStream) {
+        this.decoratedInputStream = inputStream;
+    }
+
+    @Override
+    public int read() throws IOException {
+        // 缓冲区为空时填充
+        if (position >= count) {
+            if (!fillBuffer()) {
+                return -1;  // 流结束
+            }
+        }
+        // 从缓冲区读取一个字节
+        return buffer[position++] & 0xFF;
+    }
+
+    @Override
+    public int read(byte[] b, int off, int len) throws IOException {
+        int totalRead = 0;
+        while (len > 0) {
+            // 缓冲区为空则填充
+            if (position >= count) {
+                if (!fillBuffer()) {
+                    return totalRead == 0 ? -1 : totalRead;
+                }
+            }
+
+            // 计算本次可读取的字节数
+            int available = count - position;
+            int toRead = Math.min(available, len);
+
+            // 从缓冲区复制数据
+            System.arraycopy(buffer, position, b, off, toRead);
+
+            // 更新位置和长度
+            position += toRead;
+            off += toRead;
+            len -= toRead;
+            totalRead += toRead;
+        }
+        return totalRead;
+    }
+
+    private boolean fillBuffer() throws IOException {
+        position = 0;
+        count = decoratedInputStream.read(buffer);
+        return count > 0;
+    }
+
+    @Override
+    public void close() throws IOException {
+        decoratedInputStream.close();  // 委托给被装饰对象
+        position = count = 0;  // 重置缓冲区状态
+    }
+
+    // 可选：重写其它方法提升性能
+    @Override
+    public long skip(long n) throws IOException {
+        if (n <= 0) return 0;
+
+        // 先使用缓冲区中的可用数据
+        int availableInBuffer = count - position;
+        if (availableInBuffer >= n) {
+            position += (int)n;
+            return n;
+        }
+
+        // 需要跳过超过缓冲区的内容
+        position = count;  // 消耗掉当前缓冲区
+        return availableInBuffer + decoratedInputStream.skip(n - availableInBuffer);
+    }
+}